U.S. Pat. No. 5,942,585 to Scott et al relates to clear blends of polycarbonates and polyesters where the polyester comprises a dicarboxylic acid component based on 1,4-cyclohexanedicarboxylic acid units and a glycol component comprising 2,2,4,4-tetramethyl-1,3-cyclobutanediol units. Miscible polycarbonate polyester blends are described in a Free Volume approach to the Mechanical Behaviour of Miscible Polycarbonate Blends, by A. J. Hill et al, J. Phys. Condens. Matter, 8, 3811-3827 (1996) and in Dynamic Mechanical and Dielectric Relaxation Study of Aliphatic Polyester Based Blends by Stack et al., J. M. Polym. Mater. Sci. Eng. (1993), 69, 4-5, Eastman Chemical Company, Kingsport, Tenn. 37662. U.S. Pat. No. 4,879,355 to Light et al relates to a clear polymer blend comprising a glycol copolyester having repeat units from 1,4-cyclohexanedimethanol, terephthalic acid and an alkylene glycol; a polycarbonate resin; and an aromatic polyester having repeat units from terephthalic acid, isophthalic acid and Bisphenol A. U.S. Pat. No. 4,786,692 to Allen et al. relates to a blend of an aromatic polycarbonate and a copolymer derived from a glycol portion comprising 1,4-cyclohexanedimethanol and ethylene glycol. Some of these references describe clear properties of the thermoplastic blends.
U.S. Pat. No. 5,399,661 to Borman et al relates to copolyester compositions which comprise the reaction product of at least one straight chain, branched, or cycloaliphatic C2-C10 alkane diol or a chemical equivalent and a mixture of at least two cycloaliphatic diacids. The diacid mixture comprises predominantly a trans isomer and at least one aromatic diacid. As set forth in column 5, lines 41 to 45, “The reaction is generally run with an excess of the diol component and in the presence of a suitable catalyst ***”. U.S. Pat. No. 5,486,562 to Borman et al additionally describes an impact strength modifier for compositions of the type set forth in the '661 patent.
U.S. Pat. No. 4,188,314 to Fox describes the addition of a polyester polymer derived from a cyclohexanedimethanol and a mixture of iso- and terephthalic acid to an aromatic carbonate polymer to enhance the solvent resistance as compared to a polycarbonate article.
Other references include U.S. Pat. Nos. 6,043,322; 6,037,424; 6,011,124; 6,005,059; 5,942,585; 5,194,523; and 5,017,659 and GB 1,559,230A.
Transparent blends of polycarbonate and polyesters may have attractive properties like toughness and chemical resistance. It is desirable to obtain improved properties of optical transparency and good chemical resistance without deleteriously affecting other desirable properties.